1. Field of the Invention
The present invention relates a resist material and a method of manufacturing an inkjet recording head using the resist material.
2. Related Background Art
As a resist material useful with deep-UV (UV rays of about 300 nm or shorter wavelength), polymethyl methacrylate (hereinafter referred to as “PMMA”) has been known. Also, polymethyl isopropenyl ketone (hereinafter referred to as “PMIPK”) is known as a resist material of higher sensitivity than PMMA. In addition, the specification of U.S. Pat. No. 4,297,433 discloses a sensitizing agent useful for improving the sensitivity of PMIPK.
Recently, the excimer laser has been introduced as an apparatus to take out deep-UV, and resist materials usable in the deep UV range are reevaluated. The resist materials such as PMMA and PMIPK are useful materials for micro-machining to achieve a high aspect ratio, rather than for so-called micro-patterning in the sub-micron order.
The resist materials such as PMMA and PMIPK absorb deep-UV rays, with which main chain of the polymer (called Norrish reaction) is cut so that the solubility of the resist material to a developing solution changes to enable patterning. However, the sensitivity of such resist materials is not sufficient even if the sensitizing agent disclosed in the specification of U.S. Pat. No. 4,297,433 is used together.
On the other hand, various methods have hitherto been proposed for manufacturing a head for inkjet-recording system. Japanese Patent Application Laid-Open Nos. 06-286149 and 08-323985 disclose methods of manufacturing inkjet recording heads highly suitable for obtaining high-quality images.
Japanese Patent Application Laid-Open No. 06-286149 discloses a method of manufacturing an inkjet recording head suitable for an ink ejection method disclosed in Japanese Patent Application Laid-Open Nos. 04-10940 to 04-10942 where a driving signal corresponding to recording data is applied to an ink ejection pressure generating element (electrothermal conversion element), and the electrothermal converting element generates heat energy sufficient enough to cause temperature rise over the nuclear boiling point of the ink, so that a bubble is generated in the ink, and when the bubble communicates with outside air an ink droplet is ejected.
In Japanese Patent Application Laid-Open Nos. 06-286149 and 08-323985, PMIPK or its derivative is used for the flow path pattern (a mold for the ink flow path formation). However, as described above, insufficient sensitivity of PMIPK is an obstacle in achieving a high productivity.
Lately, image quality comparable to a silver-salt photograph is required even to ink jet recording. To attain this, ink droplets as small as about 10 pico liters (pl) must be ejected with good repeatability. Thus, much finer shaping is required for nozzles.
Japanese Patent Application Laid-Open Nos. 06-286149 and 08-323985 disclose that the dimensional accuracy in nozzle formation is improved by preventing mutual dissolution between the material used for the coating resin layer where ejection openings are formed and the material used for the flow-path pattern to form flow paths. The present inventors further investigated this point to find that when ink ejection openings are is formed by photolithographic patterning of the coating resin, the shape of the ejection opening is subtly deformed due to the reflection taking place between the flow path pattern and the coating resin layer, affecting the yield.